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Primary Topic: Materials-Concrete
Description: Alkali-aggregate reactions (AAR) occur between the alkali hydroxides in the pore solution of concrete and certain minerals found in some aggregates. Two types of AAR reaction are currently recognized depending on the nature of the reactive mineral; alkali-silica reaction (ASR) involves various types of reactive silica (SiO2) minerals and alkali-carbonate reaction (ACR) involves certain types of dolomitic rocks (CaMg(CO3)2). Both types of reaction can result in expansion and cracking of concrete elements, leading to a reduction in the service life of concrete structures.
This report describes approaches for identifying deleteriously reactive aggregates and selecting appropriate preventive measures to minimize the risk of expansion when such aggregates are used in concrete. Preventive measures include avoiding the reactive aggregate, limiting the alkali content of the concrete, using supplementary cementing materials, using lithium-based admixtures, or a combination of these strategies.
FHWA Publication Number: FHWA-HIF-09-001
Publication Year: 2008
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